Some syscalls are much more likely to fail than others because
of tricky arch-dependent bits. The point here is to test for this
weak spots. Generally if write(2) fails all the time it will be
painfully obvious but if say signals do not work properly it may
take some time to figure it out just by running the tools.

Unlike other dirs, this one is pass/fail with minimum reporting.
Any debugging should involve strace anyway, so no point in trying
present the errors well.
